1. Field
The invention relates to vias and more particularly to vias used to avoid failures.
2. Related Art
Semiconductor devices often have conductors that have tabs extending laterally from sides of the conductors. These conductors are often considered buses because they are relatively wide for low resistance so as to be able to carry relatively high currents without causing problematic voltage drop. For a given technology, the depth of the lines at a given metal level is the same so that width is the variable in determining resistance per unit of length. Increasing width reduces resistance, but requires more area as well as increasing the risk of stress-induced voiding at the vias. The stress can result in a variety of failures including via failure. Although via failures may have a low probability of occurring, there are often millions of vias on a given semiconductor device. The result is that a likelihood of at least one via failure is relatively high. Thus, it has become common to provide redundant vias with the view that it is unlikely that two vias will fail at the same location. In a situation where the via is on a tab, there are limited options for a redundant via. On the other hand placing a via on the tab provides some inherent protection by distancing the via from the bus which, being wide, results in more vacancies being created.